Synthesis and solid-state supramolecular chemistry of a series of pyridinium-derived zwitterions

Abstract

A new class of potential supramolecular building blocks is presented. The synthesis and crystal structures of seven novel pyridinium-derived zwitterionic compounds are discussed, as well as two related pyridinium salts.The synthesis of these compounds was achieved by simple solution methods using mild conditions, and the products were isolated as single crystals with no further purification required. Hydrogen-bonded chains were found to be prevalent in all of the crystal structures of the zwitterions and due to the robust nature of this motif, these compounds have the potential to be exploited in future supramolecular studies. There is a large scope for the synthesis of related zwitterionic compounds using a range of pyridyl substituents with varied functional groups. These zwitterionic compounds show great potential as a new class of supramolecular building block in the formation of ionic-as well as metal-organic frameworks.Scheme 1 The general reaction scheme for the formation of zwitterions from acetylenedicarboxylic acid and various pyridyl derivatives.

Polymorphism and Host–Guest Chemistry of a Phenylpyridine-Functionalized Zwitterion

“…Zwitterion 1 exhibits interesting solvent inclusion phenomena, as well as polymorphism. As mentioned above, a methanol solvate, 1 MeOH , and a hydrate, 1 H 2 O , of this zwitterion have been previously reported . Repeating the synthesis in different solvent systems yielded two further solvates, and two polymorphs were also obtained through further experiments with the solvated structures.…”

“…We have previously reported the synthesis and structural analysis of a series of pyridyl-derived zwitterions that are stable and show potential for use as host molecules due to their unusual conformations and large number of hydrogen bonding sites. These zwitterions have the potential to form strong, directional charge-assisted hydrogen bonds, which is desirable for the formation of robust supramolecular structures.…”

“…This particular series of zwitterions can be synthesized in a straightforward manner, by combining acetylenedicarboxylic acid with various pyridyl derivatives in different solvent systems with gentle heating. The products are generally obtained as single crystals without further purification . We have previously reported detailed studies of several of these zwitterions. , Four polymorphic forms, as well as three solvates, of a benzylpyridine-functionalized zwitterion were identified, and solvent-mediated conversion between many of these forms was possible.…”

“…Because of the interesting solid-state chemistry displayed by these molecules, we have carried out a similar detailed investigation of another zwitterion from this series, (2 Z )-3-carboxy-1-hydroxy-2-(4-phenylpyridinium-1-yl)-prop-2-en-1-olate ( 1 , Scheme ). Zwitterion 1 is formed by direct reaction of acetylenedicarboxylic acid and 4-phenylpyridine in solution, as shown in Scheme . This zwitterion was previously found to form a hydrate, 1 H 2 O (Refcode: BIXNAZ), when crystallized from a 2:1 ethyl acetate/water mixture and a methanol solvate, 1 MeOH (BIXNED), when crystallized from methanol.…”

4,4′-Bipyridine-1,1′-diium acetylenedicarboxylate: a new member of the (H2bipy)[Cu(ox)2] (bipy is 4,4′-bipyridine and ox is oxalate) family

“…The compound crystallizes in the triclinic system with space group P1; the asymmetric unit contains half an H 2 bipy 2+ dication and half an ADC 2À dianion, with both H 2 bipy 2+ and ADC 2À located on crystallographic inversion centres. The difference between the two C-O distances (Ár) in (1) amounts to 0.0458 (15) Å [1.2237 (15)/1.2695 (15) Å ], less than that in acetylenedicarboxylic acid in its cocrystal form (Loots et al, 2014;Mei & Wolf, 2004). The internal angle of the pyridine ring, C5-N1-C1, is 120.56 (10) , larger than the corre-sponding angle in the neutral 4,4 0 -bipyridine molecule [e.g.…”